I have a USB mic and would like to record from in a padded closet roughly 30 feet away from the computer.

I read that buying a 30ft cable will not work, but is there anyway around this?

According to Wikipedia: USB 2.0 provides for a maximum cable length of 5 meters for devices running at Hi Speed (480 Mbit/s). The primary reason for this limit is the maximum allowed round-trip delay of about 1.5 μs.

So how do these USB cable extenders work then? Will one of these extenders work with my USB mic?

I do not think a mic really needs full 480 Mbit/s transfer rates, however the delay is a factor. Considering a powered USB extension cable only costs $8.50 plus shipping I would just say go ahead and try it and report back.

Make sure whatever you get is called either Active or Powered, it basically acts as a 1 port USB hub.

If the delay turn out to be a problem you can use a 'USB mic with build in sound card' (e.g. a blue yeti, though I am reluctant to mention what seems like shopping advice. It is just the Mic I looked at a while ago)
–
HennesJul 20 '12 at 18:20